1. Field of the Invention
The present invention relates generally to seals, and more particularly to, a seal adapted to be disposed about a cylindrical shaft.
2. Description of the Related Art
Currently, seals are disposed about shafts such as a pinion shaft of an automotive vehicle. These seals typically have a lip surface which contacts the shaft. However, one problem with these seals is that if contact stress at the lip surface is generally high, a lubricant film formed on the lip surface tends to be squeezed out of the lip surface.
One attempted solution to this problem is to provide seals having a textured lip surface. An example of a seal having a textured lip surface is found in German Patent No. 3612-420-A. The textured lip surface reduces turning torque of the seals by retaining a lubricant film in a random pattern of texture.
One problem of conventional seals having textured lip surfaces is that the lubricant film may escape when the seal is subjected to pressure that squeezes the lip surface onto the shaft surface, thus flattening out some of the texture. Conventional seals having textured lip surfaces may also allow the lubricant film to escape when the lubricant viscosity is reduced (e.g., under high temperature conditions).
Another problem of conventional seals involves seals assembled in equipment and then stored for a period of time. Over time, contact stress at the lip surface squeezes any lubricant film out, and when the shaft is first moved, a high turning torque on the seal is experienced.